Surface-mount technology (SMT) is a manufacturing method for mounting an active or passive electronic component, such as a resistor, capacitor, inductor or semiconductor chip, onto the surface of a printed circuit board (PCB). The electronic component has leads or contacts, herein collectively referred to as leads, used to interconnect with corresponding contact points, such as solder pads, on the PCB. Examples of such leads include, but are not limited to, short pins or leads of various styles, flat contacts, a matrix of solder balls, or terminations on the body of the component.
To mechanically and electrically attach the electronic component to the PCB, solder paste is first applied to the solder pads on the PCB. A pick and place machine then places the electronic component on the PCB such that the leads of the electronic component are aligned and in contact with the corresponding solder pads on the PCB. The PCB is then conveyed into a reflow soldering oven where the temperature is high enough to melt the solder paste, bonding the leads of the electronic component to the solder pads on the PCB.
Through-hole technology is another manufacturing method for mounting an electronic component on a PCB. Leads of the electronic component are inserted into holes drilled through the PCB and soldered to pads on the opposite side. A wave soldering process is used to apply the solder. The wave soldering process includes a preheating step that heats the PCB.
Heating the PCB during the solder reflow step or the preheating step subjects the electronic component to thermal heat exposure. Some electronic components, such as aluminum electrolytic capacitors, are highly sensitive to thermal heat exposure. For such electronic components, the temperature needed to bond the leads to the PCB exceeds the temperature that results in damage to the body of the electronic components. In the case where the electronic component is an aluminum electrolytic capacitor, for example, the capacitor body must stay below 200 degrees Celsius while the leads must be above 230 degrees Celsius for a minimum of 30 seconds to perform the solder paste reflow process.
Existing material properties and/or combinations provide limited thermal protection to the electronic component. Using different materials and shapes has proven to be extremely challenging to find the best combination and design to achieve the thermal targets required.